1. Field of the Invention
The present invention generally relates to controllers. In particular, the present invention relates to a controller of an optical disk device.
2. Description of Related Art
In recent years, optical disks have been extensively developed as a means for storing a large amount of data. Optical disk devices use laser beams for recording data to or reproducing data from the optical disks.
Referring to FIG. 10, a schematic diagram of an optical disk device is shown. Generally, the optical disk device 90 includes a spindle motor 92, an optical pickup unit 94, a servo unit 96, and a controller 98.
The spindle motor 92 has a rotor 922 on which an optical disk 100 may be placed, and is used for driving the optical disk 100 to rotate around an axis of the rotor 922. The optical pickup unit 94 is configured for emitting a laser beam to the optical disk 100, receiving a return laser beam reflected from the optical disk 100, and converting the return laser beam into electric signals. The electric signals may include data-signals containing data recorded on the optical disk 100, and servo error signals of the optical pickup unit 94. The controller 98 receives the electric signals from the optical pickup unit 94 and generates servo-adjusting signals based on the servo error signals. The servo adjusting signals are transmitted to the optical pickup unit 94 and the servo unit 96 for performing focusing and/or tracking to eliminate or decrease focus and/or tracking error between the optical pickup unit 94 and the optical disk 100.
Referring now to FIG. 11, a block diagram illustrating an example of a controller used in an optical disk device is shown. The controller 110 includes a low pass filter 112, a first notch filter 114, a lead-lag controller 116, and a second notch filter 118. The low pass filter 112 is used for depressing high frequency components of inputted signals, and thus reducing control efforts caused by the high frequency components. The first notch filter 114 is collocated at a corresponding rotation frequency of a given optical disk, in order to give a large local gain at the rotation frequency. The lead-lag controller 116 is used for filtering at a relatively low frequency and maintaining a stable filtering loop. The second notch filter 118 is in correspondence with a resonance frequency of a given optical pickup unit and servo unit. See, for example, Sergio Bittanti, Fabio Dell'Orto et al. “RADIAL TRACKING IN HIGH-SPEED DVD PLAYERS (an application of notch filtering and multirate control)”, Proceedings of the 40th IEEE conference on Decision and Control, Orlando, Fla. USA, December 2001.
However, the above mentioned article fails to give an example of an apparatus for calibrating parameters of the controller 98 when the controller 98 is utilized with a controlled plant, such as an optical pickup, and a tracking servo unit. Whereas, due to different characteristics of the controlled plant, parameters of the controller should be calibrated to generate controlling signals accurately. Otherwise the controller is not adaptable with different controlled plants. Therefore, a need exists in the industry for an apparatus for calibrating controller parameters for different controlled plants of different optical disk devices.